There have long been speculations that the Portal universe and the Half-Life universe are the same and that the game is actually connected but Valve has never confirmed or denied those rumors but we are not going to talk about that here.
While it will be interesting if these two games were actually connected, what we are talking about is the fact that the Portal fans will eventually join the Half-Life fans in their never-ending wait for a game that will never arrive.
The ending in Portal 2 suggest that there might be more to the story and even though Valve has never suggested that there might a sequel, most fans believe there is. However, after years of waiting, it still does not feel like a Portal 3 is going to happen.
Some people think that Valve will release a game that is both Half-Life 3 and Portal 3 soon but we are not sure that is ever going to happen.